2018 BMW 5-Series Prototype - Refocusing on Dynamics

The benchmark sports sedan finds the Welsh road to recovery

Here at european car, we've attended our fair share of new model pre-drives where the vehicles under test are labelled "pre-production," and they're often plastered with swirly black and white camouflage to trick our eyes into not seeing what's underneath. And yet you can tell that they're not far off the finished article, even if we're routinely told to ignore any issues we find as they'll "be ironed out by the time the car goes into production." Today is a little different. Today we've met up with the chassis development team working on the next-generation BMW 5 Series a full five months before the car's design will be revealed to the public, and we're told in no uncertain terms that we're to ignore everything about the hard-used development mules we'll be driving-other than the chassis dynamics. This promises to be very interesting.

Obviously, it's impossible to ignore the rest of the car. Even through the camouflage, we can see that the new 5 Series will be less bulbous in appearance and tauter in line, helping to visually shrink the car. Inside, the prototypes wear more disguise, along with extra testing equipment. It's clear that there's plenty of influence from the BMW 7 Series in the cabin of the new Five. Expect similar instrumentation ahead of a tactile new steering wheel and the same driving mode selector as found in the Seven. The graphics on the large iDrive screen, meanwhile, should also be carried over from the bigger car. Interior space feels on par with the current F10 generation.

Curiously, there's more to this driving opportunity that BMW has asked us to omit. We can mention we are in North Wales, but the personnel would really rather we didn't specify which roads we use for the day's testing. The reason is that this crack team of lead development engineers travels from Munich to this area twice a year to test their cars. It's one of the few on-road locations used as part of the suspension and development sign-off program. Obviously, tracks such as the Nürburgring in Germany are also employed, but, after consultation with BMW U.K., the engineers realized that the Welsh roads are an ideal test ground. Jos van As, vice president application driving dynamics BMW Group, tells us that this area has a wide variety of roads on which to test, with wicked twists and turns and highly challenging bumps. The road surface itself has plenty of grip, too, even in the wet and, as a final bonus, it's a quiet part of the world, even in tourist season. The team has been coming to the same area and even staying in the same hotel for a number of years now, and they've yet to be bothered by outside influences.

After a short chat about the car, they waste no time in getting us out on those roads. First up is the BMW 540i, presumably powered by the same turbocharged straight-six used in the recently launched 340i. It's paired with the usual eight-speed automatic transmission and we've got a rear-drive version. Personnel on hand refer to it as a 540i sDrive, so it'll be interesting to see if that name is applied to all-rear-drive versions of the 5 Series from now on. The prototype also has Variable Damping Control and Integral Active Steering. Although we are to be accompanied for the whole day by a selection of engineers, rather surprisingly, we are doing all the driving. To help us "optimize" the driving routes, there'll be a lead car driven by one of the other engineers. He's clearly very very familiar with the Welsh roads, so we're soon maintaining a decent cross-country pace.

There's no wrapping the car in cotton wool, either, as we pound over nasty bumps, scythe through well-sighted switchbacks, and rattle over endless cattle grids. In between focusing on keeping the well-driven X5 ahead in sight, we quiz Manfred Ahrens, functional design driving dynamics BMW 5 Series, about the new car. They don't want to say too much until the official "start of communication" in October, but we do learn that the new "G30" 5 Series is about 200 pounds lighter than before. Aluminium is used for the roof, doors, and boot lid, while high-quality steel makes up most of the car's structure, with magnesium for the rear of the dashboard. Why not more carbon as used in the 7 Series? It's just not practical or economic at this stage: One year of production numbers for the 5 Series, for example, is about the same as the whole life cycle of the 7 Series.

Regardless, BMW has also managed to reduce the 5 Series' center of gravity by "a few millimeters," which should help the car's dynamic performance. Indeed, when asked about the focus of attention for the new car, we're given a very clear answer: "In the F10, we achieved a very good level of comfort. That car was very successful. Now we want to maintain that comfort and focus once more on dynamics, while keeping the car balanced. The technology focus on BMW over the past two decades has been first on EfficientDynamics, then BMW I, and even autonomous driving. Now we are refocusing on dynamics, something that is core to the brand."

Our first hour at the wheel reveals that BMW may well have nailed its own brief. Variable ratio steering racks aren't liked by all, but this one feels natural and endows the big Five with a particularly agile stance. It never seems to take too much lock to get through a corner, and there's good feedback, too. The body control is excellent in each of the variable damping modes, though we manage to hit the bumpstops on one particularly challenging downhill section described by Jos van As as "the Nürburgring with lines down the middle-and sheep." It's a split second thing, and the car is being driven quickly, but they take it very seriously and discuss it in depth later on.

Apparently, the suspension on these cars is 90 percent finished. When testing in Wales, the engineers don't have access to a specialized workshop or a truck full of spares, so they restrict their adjustments to what they can alter via a laptop. Essentially, that means the electrically assisted power steering and the damping, if a variable system is fitted. We're told these roads are not used for scientific testing, but instead they are looking for how the car feels, whether it is agile enough, and whether body control is good enough.

Next up, we're into a 530d xDrive model with four-wheel drive and the same eight-speed automatic transmission. This vehicle also has Integral Active Steering, but it's paired with sports suspension. That means lower springs and firmer dampers, but no adjustablability. It turns out to be our favorite steer of the day. Even though the 540i's adaptive damping theoretically offers more options, the sports suspension fitted to this 530d seems the perfect setup and it coped well with a wide variety of surfaces and bumps without ever feeling harsh or rigid. The weather was bright and warm so we didn't really need or even notice the xDrive four-wheel-drive system at work.

When stopped for a breather, I notice the run-flat tires and this starts an interesting conversation. It's admitted that the very first implementation of the run-flat tires wasn't great, as knowledge and experience with them was still in its infancy. Back then, the cars were developed with normal tires, and then run-flats were fitted in production, which is madness given that the tire is the first "spring" in the suspension system. Now, BMW is confident it has a handle on them, and they're used from day one in the development process. Not only that, but the run-flat tire design has come on leaps and bounds. At the start, the sidewalls were incredibly stiff to allow the cars to drive for nearly 200 miles on a flat, but those stiff sidewalls ruined ride comfort. It has since been decided that there's little need for such a long range, allowing less compromise in the tire construction. While Johann Kistler, project director BMW 5 Series, admits there's still a reason BMW M use normal tires for dynamics and engagement, he claims the run-flat alternatives are not too far behind. And now customers don't want to do without them, especially in the U.K. and America. They like the security of not having to stop at the side of a road when they have a puncture.

Our final drive of the day is in a rear-drive 530i, but instead of piling around the Welsh countryside behind a pace car, we're going to get a little hands-on experience of what the engineers do. Alexander Meske, head of application driving dynamics BMW 5 Series, accompanies us with a laptop and we discuss steering in depth. The 530i has standard steering and suspension and it feels supple and good to drive. The body control isn't quite as taut as it was in the 530d with sports suspension, but it is definitely a step up from the outgoing F10's standard suspension in that regard. Interestingly, BMW optimizes the spring and damper rates for each of the three suspension systems for the wheel and tire combination that are most likely to be used. So the sports suspension, for example, is optimized for larger wheels, while the standard "comfort" suspension has been set up on the smallest wheels offered.

We go back and forth over the same 5-mile stretch for an hour or so, stopping to change the power steering calibration each time. It's an illuminating experience, revealing just how much influence the power steering system can have over the feel of the car. At the extremes, Meske demonstrates dull, "sludgy" responses, making the 5 Series feel heavy and unwieldy, then overly light steering with no resistance to you turning the wheel at the other end of the spectrum. The optimum setting in the middle gives the driver information as the wheel is turned while still making the car feel agile, and yet the steering can't be too heavy or it will tire the driver out. I don't envy his task in finding the perfect balance, as every driver has a preference. Indeed, an American colleague later in the day preferred the heavy, low-assistance setup that I thought made the 5 Series feel unwieldy. There is no scientific way to set it up "correctly" after all.

And indeed, while a huge amount of modern car engineering is carried out using computers, they can't hope to replicate the experience of driving on real, challenging roads. It's quite heartening to know that a little bit of Wales is in every BMW 5 Series made. We can't wait to try out the finished article in November.